Many treatment jobs require electrodes which are suitable for being rolled over the tissue so as to achieve a homogeneous success of treatment over a major area:
From the German Patent DE 42 42 126 C1, for instance, an electrode for HF surgery has become known. That known electrode comprises a body of revolution which presents projections on its surface which sink into the endometrium and which are specifically configured in the form of spikes. As a result of the projections on the body of rotation, which sink into the tissue, the greatest current density is intended to be achieved in the depth of the tissue rather than on the surface.
Similar electrodes are known from the U.S. Pat. No. 5,395,363 or from the laid-open German Patent Application DE-OS 22 22 820.
In a number of cases, however, a penetration of the electrode body into the tissue is undesirable. In another HF surgery electrode of the claimed general type, the electrode body is therefore provided with recesses rather than projections so that a specific current distribution is achieved even though the electrode does not sink into the tissue on account of these recesses. In this respect reference is made to the German Utility Model DE 295 11 618 U1.
With this configuration, however, disadvantages are entailed in practical application, such as a higher risk of injury due to the shoulders or recesses in which tissue fragments could "get caught".
The invention is therefore based on the problem of providing an electrode for HF surgery, and particularly for vaporising tissue, which comprises an electrode body rolling over the tissue and suitable to achieve a certain distribution of current density without occurrence of the disadvantages linked up with the use of projections or recesses, respectively.
One inventive solution to this problem is solved by an electrode having its body formed with a plurality of regions with high and low electrical conductivity which constitute a smooth surface of the body.
The invention deviates from the obviously generally prevailing view about electrodes of the claimed general type, which comprise at least one rolling electrode body, that merely an electrode body provided with projections or recesses could ensure the desired distribution of current flow and hence the desired success of the treatment.
In accordance with the invention an electrode is provided which comprises at least one electrode body rolling over the tissue and having a smooth surface in contact with the tissue, which is smooth. In the smooth surface regions of low electrical conductivity or insulating regions and a plurality of regions which are not coherent in the surface, which present a high electrical conductivity. The regions of high electrical conductivity may be combined to form one or several groups, with the regions of each group being interconnected inside the electrode body or outside the electrode body in an electrically conducting way.
The connection may be made in such a form that all the regions are interconnected--which means that only one group is provided--so that an electrode operating in a monopolar way is obtained.
It is moreover possible that the electrically conducting regions are combined to form at least two groups interconnected each inside the electrode body so that the electrode presenting such an inventive structure may be employed as bipolar electrode.
In accordance with a further aspect of the invention the regions of low electrical conductivity are preferably made of an electrically insulating material.
Since the individual regions account for a defined share of the surface it is possible to adjust a defined distribution of current density.
A further aspect of the invention discloses the electrode body comprising an electrically conducting central region having projection extending towards the smooth surface which comes into contact with the tissue. The areas between the projections are filled with a material of low electrical conductivity or with insulating properties, respectively, so that the smooth surface employed in accordance with the invention is achieved. The surface regions with a good electrical conductivity or with insulating properties, respectively, may be arranged with a statistic distribution or in a regular array. Which of the two possibilities is actually selected depends on the respective medical application.
In the event of regularly arranged projections the central region may present longitudinal and/or transverse grooves and/or projections extending towards the smooth surface, depending on the medical indication of the respective different possibilities and/or on the least complex production possible in terms of manufacturing engineering.
In any case, however, it is preferred that the entire planar extension of the regions with good electrical conductivity is smaller than the extension of the regions with poor electrical conductivity because with such a configuration a distribution of the current density is achieved which is particularly well suitable for vaporisation.
The fundamental idea of the inventions is to use an electrode body with a smooth surface in which merely one part of the surface contributes to the flow of current and may be applied to different electrodes.
The electrode body may, for instance, present the shape of a cylinder or of a ball, which parts are supported for rotation so that the electrode may be moved over the tissue in a rolling motion, and it may be applied to electrode bodies presenting the shape of a plate or a tape which is bent in at least one direction.
The safety for the patient is increased by utilizing the material of low electrical conductivity or with insulating properties, respectively, connected by a positive connector to the central electrode body so as the risk is reduced that some detached material may deposit in the body.
According to still another aspect of the invention, a method for making an electrode having a smooth surface which is provided with a different electrical conductivity is also provided.
The method of producing an electrode, initially an electrode body is manufactured which presents at least one electrically conducting region, in which recesses are formed in that surface region which comes into contact with the tissue to be treated. The recesses are filled with a material of poor electrical conductivity so that a smooth surface is created. To this end a coating process or a vapour deposition process may be employed. After the recesses have been filled the electrode may be machined, for instance, at least in that part of the surface which comes into contact with the tissue to be treated. This produces a defined surface which is smooth in correspondence with the selected machining operation.
Still another aspect of the invention describes undercuts which are provided in the recesses in the electrode body so that the material of low electrical conductivity will adhere to the electrode body in a positive locking action. This enhances the safety level for the patient--as has been set out above. In any case, the inventive configuration of the electrode body leads to surprising advantages over both the common rolling electrode bodies with projections or recesses and electrode bodies in a rigid arrangement and having a smooth surface with regions of different conductivity, which are distributed in the surface--in this respect reference is made to the U.S. Pat. No. 3,460 539: Compared to this prior art a particularly homogeneous and efficient application of HF current to the tissue is achieved due to the rolling motion of the smooth surface, including areas of different conductivity, on the tissue.